1. Field of the Invention.
The present invention relates to a syringe and more particularly concerns a two-component syringe.
2. Description of the Prior Art.
Some injectable medications have rapid loss of potency when they are in their ready-to-use form. In order to protect against the short shelf life of these medications, many of them are supplied in two-components, and they are mixed at the time of use. Two-component medication is commonly available in two vials with pierceable stoppers. A first vial typically contains a diluent such as sterile water and the second vial contains the active ingredients which may be in, for example, lyophilized form. To prepare the medication for use, the user pierces the stopper of the vial containing the water with a sterile syringe and needle assembly and withdraws the water into the syringe. The needle is then removed from the first vial and inserted into the second vial. Water is injected into this vial to mix with the lyophilized medication. The mixed medication is then withdrawn into the syringe for injection. When the injection is to be made into a vein, it is common practice to insert the needle into the patient and to withdraw the plunger rod slightly from the syringe barrel. If the needle is in a vein, a slight amount of blood will be drawn into the syringe. The visual sighting of the blood verifies that the needle is in a vein. This procedure is called the vein indication test. Also, when injection of medication into a vein or artery is not desirable, the vein indication test can be used to assure that the hypodermic needle is not in a vein or artery.
Use of the above-recited separate vials presents problems with respect to sterility since only the interior of the medication vial is sterile and bacteria from the exterior of the vials and the environment may be introduced into the medication during the mixing procedure. Also, at the areas where the cylindrical surfaces of the lumen of the hypodermic needle intersect the planes of its ground point, there are formed sharp edges that can potentially cut pieces of the rubber vial stopper away as the needle penetrates it. It should be noted that the potential for generating rubber particles varies between different needle point configurations. These pieces of rubber represent a potential health hazard if they pass along with the liquid medication into the patient's body. Further, cost is high since two separate sterile containers and a sterile syringe are normally required.
Brown (U.S. Pat. No. 2,607,344) teaches placing both components of the medication in a glass tube in which the components are separated by a stopper with a piston stopper sealing the end of the tube containing a liquid component and a flanged pierceable stopper sealing the end of the tube containing a powder component. Also, within the powder containing compartment, bounded by the stopper and the pierceable stopper, there is a longitudinally positioned groove projecting radially outwardly enlarging the inside diameter of the glass tubing. The groove is longer than the stopper so that when the stopper is positioned within the section of the tube containing the groove, liquid can flow around the stopper through the groove. Also provided is a separate barrel having an open proximal end adapted to accept the glass tube assembly and a distal end with a wall containing a cannular with opposed points. One end of the cannula projects into the barrel, and the other end projects outwardly away from the distal end of the barrel.
In use, the tube assembly of Brown is inserted into the barrel so that the portion of the cannula inside the barrel penetrates the pierceable stopper establishing fluid communication between the interior of the tube and the atmosphere. Then the piston stopper is forced inwardly pushing the liquid component of the medication and the stopper toward the distal end of the barrel. When the stopper is positioned within the by-pass, the liquid component flows around the stopper through the by-pass to mix with the powder component. To perform the vein indication test, the tube is withdrawn to terminate fluid communication with the cannula and then the outwardly facing portion of the cannula is inserted into the patient. Since the flange of the pierceable stopper is larger than the inside diameter of the barrel, further withdrawal of the tube from the barrel creates a reduced pressure zone between the exterior end of the pierceable stopper and the cannula causing blood to flow from the cannula into the barrel, outside of the tube assembly, if the cannula is lodged in a vein.
Genese (U.S. Pat. No. 4,226,236) teaches placing a liquid diluent and a solid medicament in a syringe barrel wherein the liquid diluent is contained between two stoppers and the solid medication is contained between one of the aforementioned stoppers and a hydrophobic filter which Genese suggests will not allow liquid to pass therethrough. This syringe contains an outwardly projecting by-pass on the side of the barrel. To mix the medicament and the diluent the user removes a ferrule and the closure cap on the distal end of the syringe assembly and then pushes the plunger rod, which is attached to the first stopper, inwardly. The movement of the first stopper forces the diluent and the intermediate stopper in a forward direction until the intermediate stopper is positioned in the area of the by-pass, and the diluent is then forced around the intermediate stopper through the by-pass and onto the solid medicament. It appears that when the diluent contacts the hydrophobic filter, no air or water is permitted to pass and, further, that whatever air remains in the syringe after the diluent contacts the hydrophobic filter is trapped within the syringe and cannot escape.
At this point, Genese teaches that the syringe is to be shaken to cause mixing of the two components. To use this syringe, a slidably mounted hollow piercing member is moved rearwardly to puncture the hydrophobic filter and to allow fluid communication between the interior of the syringe barrel and the interior of the hollow piercing member. The distal end of the slidable piercing member is shaped to allow attachment of a hypodermic needle assembly. With the hypodermic needle assembly attached, the remaining air and mixed medication can be expelled from the syringe. The Genese syringe has deficiencies in that it requires the puncturing of a syringe component in order to deliver the medication to the patient, and therefore it has the potential for generating foreign particles which could be injected into the patient. Further, Genese offers no teaching with respect to the vein indication test and the Genese syringe is complex having approximately 12 individual components. It also appears that the syringe taught by Genese will function only if the medication component between the stopper and the filter is not a liquid because the liquid in this area would seal the hydrophobic filter preventing air from escaping the preventing the movement of the stopper into the by-pass area.
It is undesirable to have a stopper or filter element within the syringe that must be punctured before medication can be discharged from the syringe because the puncturing can produce potentially harmful particles or debris which can then be injected into the patient. However, in the case of the syringe taught by Genese, if the filter were removed, the liquid may have a tendency to squirt from the by-pass directly into and/or out of the tip of the syringe. Accordingly, it is desirable to provide a two-component medication syringe which is configured to minimize loss through the syringe barrel tip while providing for the thorough mixing of the two medication components.
Presently pending U.S. patent application Ser. No. 536,927, filed Sept. 28, 1983, having a common Assignee herewith, also describes a two-component medication syringe.
Apparatuses and methods for the storage, mixing and administering of two-component medication have been addressed by the prior art, as alluded to, above. However, there is still a need for a simple, straightforward, reliable, easily fabricated syringe assembly for the storage, mixing and administering of two-component medications wherein one or both components are in liquid form. It is desirable that the syringe assembly minimize contamination potential by allowing the mixing and administering steps to be performed without puncturing stoppers or other barriers within the syringe or transferring the medication components through non-sterile barriers which are exterior to the syringe assembly. It is desirable that the syringe be configured to minimize medication loss during mixing and to promote thorough mixing of the medication components. It is also desirable that the syringe assembly be capable of easily performing the vein indication test.